Match service argument names to abstract interface (#9418)

The base class/documentation suggest that the argument
names are `self` and `done`, while the runtime used
argument names `srvc` and `callback`.

`mypy.stubtest` was able to identify this - as it compares
the types (autogenerated by
[`mypy-protobuf`](https://github.com/dropbox/mypy-protobuf/))
to the actual code generated by protoc at runtime.

Since the stubs assume the generated code matches the abstract
interface in service.py - it saw these differences.

CONTRIBUTORS.txt

@@ -100,3 +100,8 @@ Patch contributors:
   Andrew Paprocki <andrew@ishiboo.com>
     * Fixed minor IBM xlC compiler build issues
     * Added atomicops for AIX (POWER)
+  Nipunn Koorapati <nipunn1313@gmail.com>
+    * Provide a type alias field ValueType on EnumTypeWrapper
+    * Match service argument names to abstract interface
+
+

python/google/protobuf/service_reflection.py

@@ -133,7 +133,7 @@ class _ServiceBuilder(object):
     """
     self.descriptor = service_descriptor
 
-  def BuildService(self, cls):
+  def BuildService(builder, cls):
     """Constructs the service class.
 
     Args:
@@ -143,18 +143,25 @@ class _ServiceBuilder(object):
     # CallMethod needs to operate with an instance of the Service class. This
     # internal wrapper function exists only to be able to pass the service
     # instance to the method that does the real CallMethod work.
-    def _WrapCallMethod(srvc, method_descriptor,
-                        rpc_controller, request, callback):
-      return self._CallMethod(srvc, method_descriptor,
-                       rpc_controller, request, callback)
-    self.cls = cls
+    # Making sure to use exact argument names from the abstract interface in
+    # service.py to match the type signature
+    def _WrapCallMethod(self, method_descriptor,
+                        rpc_controller, request, done):
+      return builder._CallMethod(self, method_descriptor,
+                       rpc_controller, request, done)
+    def _WrapGetRequestClass(self, method_descriptor):
+      return builder._GetRequestClass(method_descriptor)
+    def _WrapGetResponseClass(self, method_descriptor):
+      return builder._GetResponseClass(method_descriptor)
+
+    builder.cls = cls
     cls.CallMethod = _WrapCallMethod
-    cls.GetDescriptor = staticmethod(lambda: self.descriptor)
+    cls.GetDescriptor = staticmethod(lambda: builder.descriptor)
     cls.GetDescriptor.__doc__ = "Returns the service descriptor."
-    cls.GetRequestClass = self._GetRequestClass
-    cls.GetResponseClass = self._GetResponseClass
-    for method in self.descriptor.methods:
-      setattr(cls, method.name, self._GenerateNonImplementedMethod(method))
+    cls.GetRequestClass = _WrapGetRequestClass
+    cls.GetResponseClass = _WrapGetResponseClass
+    for method in builder.descriptor.methods:
+      setattr(cls, method.name, builder._GenerateNonImplementedMethod(method))
 
   def _CallMethod(self, srvc, method_descriptor,
                   rpc_controller, request, callback):